iOS如何将字符串中特定后的字变成红色

- (void)viewDidLoad {  [super viewDidLoad];  // Do any additional setup after loading the view, typically from a nib.  UILabel *testLabel=[[UILabel alloc]initWithFrame:CGRectMake(10, 100, 100, 50)];  testLabel.text=@"1234567890";  testLabel.backgroundColor=[UIColor orangeColor];  [self.view addSubview:testLabel];  [self redXingWithLabel:testLabel atIndex:2];}//将字符串特定的1个字变成红色- (void)redXingWithLabel:(UILabel *)tempLabel atIndex:(NSInteger)tempIndex {  NSMutableAttributedString * tempString = [[NSMutableAttributedString alloc] initWithString: tempLabel.text];  [tempString addAttribute:NSForegroundColorAttributeName value:[UIColor redColor] range:NSMakeRange(tempIndex, 1)];  tempLabel.attributedText = tempString;}